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Fix initialization of spinlock in irttp_dup()

PATCH In review Deepak Saxena 3 participants 3 messages Mar 20, 2007 – Mar 21, 2007

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Deepak Saxena

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#0 lore raw

PATCH 1/1 Fix initialization of spinlock in irttp_dup()

This was found around the 2.6.10 timeframe when testing with the -rt patch and I believe is still is an issue. irttp_dup() does a memcpy() of the tsap_cb structure causing the spinlock protecting various fields in the structure to be duped. This works OK in the non-RT case but in the RT case we end up with two mutexes pointing to the same wait_list and leading to an OOPS. Fix is to simply initialize the spinlock after the memcpy().

Signed-off-by Deepak Saxena <[email protected]>
net/irda/irttp.c +1 -0
index a7486b3..df2b2f7 100644
@@ -1441,6 +1441,7 @@ struct tsap_cb *irttp_dup(struct tsap_cb
 	}
 	/* Dup */
 	memcpy(new, orig, sizeof(struct tsap_cb));
+	spin_lock_init(&new->lock);
 
 	/* We don't need the old instance any more */
 	spin_unlock_irqrestore(&irttp->tsaps->hb_spinlock, flags);
Signature · 4 lines
Deepak Saxena - [email protected] - http://www.plexity.net

In the end, they will not say, "those were dark times,"  they will ask
"why were their poets silent?" - Bertolt Brecht
#1 lore raw

Hi Deepak,

Quoted 6 lines · Deepak Saxena

This was found around the 2.6.10 timeframe when testing with the -rt patch and I believe is still is an issue. irttp_dup() does a memcpy() of the tsap_cb structure causing the spinlock protecting various fields in the structure to be duped. This works OK in the non-RT case but in the RT case we end up with two mutexes pointing to the same wait_list and leading to an OOPS. Fix is to simply initialize the spinlock after the memcpy().

This has just made it to the netdev and stable trees. See:
http://git.kernel.org/?p=linux/kernel/git/davem/net-2.6.git;a=commit;h=7bb1bbe615de25d955b974cb47d40fa198154bb9

Cheers,
Samuel.

Quoted 21 lines
Signed-off-by Deepak Saxena <[email protected]>
net/irda/irttp.c +1 -0
index a7486b3..df2b2f7 100644
@@ -1441,6 +1441,7 @@ struct tsap_cb *irttp_dup(struct tsap_cb
 	}
 	/* Dup */
 	memcpy(new, orig, sizeof(struct tsap_cb));
+	spin_lock_init(&new->lock);
 
 	/* We don't need the old instance any more */
 	spin_unlock_irqrestore(&irttp->tsaps->hb_spinlock, flags);
Signature · 5 lines
-- 
Deepak Saxena - [email protected] - http://www.plexity.net

In the end, they will not say, "those were dark times,"  they will ask
"why were their poets silent?" - Bertolt Brecht
#2 lore raw
In reply to Deepak Saxena
Quoted 7 lines · Deepak Saxena

This was found around the 2.6.10 timeframe when testing with the -rt patch and I believe is still is an issue. irttp_dup() does a memcpy() of the tsap_cb structure causing the spinlock protecting various fields in the structure to be duped. This works OK in the non-RT case but in the RT case we end up with two mutexes pointing to the same wait_list and leading to an OOPS. Fix is to simply initialize the spinlock after the memcpy().

note that memcpy based lock initialization is a problem for lockdep too.

Ingo